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The ifDefined directive should return a non-null type, not just non-undefined. #296

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The ifDefined directive should return a non-null type, not just non-undefined. #296

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4cc6d91
The `ifDefined` directive should return a non-null type.
bicknellr Jan 11, 2023
942db29
`ifDefined` in Lit 2 also drops `null`.
bicknellr Jan 12, 2023
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12 changes: 9 additions & 3 deletions packages/lit-analyzer/src/lib/rules/util/directive/get-directive.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,7 @@ import { HtmlNodeAttrAssignment, HtmlNodeAttrAssignmentKind } from "../../../ana
import { RuleModuleContext } from "../../../analyze/types/rule/rule-module-context.js";
import { lazy } from "../../../analyze/util/general-util.js";
import { removeUndefinedFromType } from "../type/remove-undefined-from-type.js";
import { isLitDirective } from "./is-lit-directive.js";
import { isLit1Directive, isLitDirective } from "./is-lit-directive.js";

export type BuiltInDirectiveKind =
| "ifDefined"
Expand Down Expand Up @@ -48,8 +48,14 @@ export function getDirective(assignment: HtmlNodeAttrAssignment, context: RuleMo
// This new type becomes the actual type of the expression
const actualType = lazy(() => {
if (args.length >= 1) {
const returnType = toSimpleType(checker.getTypeAtLocation(args[0]), checker);
return removeUndefinedFromType(returnType);
const exprType = toSimpleType(checker.getTypeAtLocation(assignment.expression), checker);

if (isLit1Directive(exprType)) {
const returnType = toSimpleType(checker.getTypeAtLocation(args[0]), checker);
return removeUndefinedFromType(returnType);
}

return toSimpleType(checker.getNonNullableType(checker.getTypeAtLocation(args[0])), checker);
}

return undefined;
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8 changes: 8 additions & 0 deletions packages/lit-analyzer/src/test/rules/no-nullable-attribute-binding.ts
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Expand Up @@ -25,3 +25,11 @@ tsTest("Can assign 'null' in property binding", t => {
const { diagnostics } = getDiagnostics('html`<input .selectionEnd="${{} as number | null}" />`');
hasNoDiagnostics(t, diagnostics);
});

tsTest("Return type of `ifDefined` is not `null`", t => {
const { diagnostics } = getDiagnostics(`
const ifDefined = <T>(x: T) => x ?? "non-null";
html\`<input some-attribute="$\{ifDefined(Math.random() < 0.5 ? 123 : null)}" />\`;
`);
hasNoDiagnostics(t, diagnostics);
});